A number of reports have already been made on the process for producing olefin polymers using a metallocene complex. For example, JP-A-58-19309 discloses a process for producing olefin polymers which uses a metallocene complex and an aluminoxanone. The process has a problem in that when olefin is polymerized with the disclosed catalyst which uses bis(cyclopentadienyl)zirconium dichloride and methylaluminoxane, the molecular weight of the olefin polymer obtained is low. To improve this point, WO87/02370 discloses the use of a reaction product of an organic compound having at least two hydroxyl groups with a transition metal compound. However, the system disclosed in WO87/02370 which uses 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride and methylaluminoxane, and also a system disclosed in JP-A-5-230133 which uses 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride, triisobutylaluminum and triphenylmethyl tetrakis(pentafluorophenyl)borate involve a problem in that the catalytic activity is unsatisfactorily low from the industrial point of view although the molecular weight of the polymer produced is improved.
Moreover, known metallocene complexes, e.g., ethylenebis(indenyl)zirconium dichloride, isopropylidene(cyclopentadienyl) (fluorenyl)zirconium dichloride and dimethylsilyl(tert-butylamide)-(tetramethylcyclopentadienyl)titanium dichloride, have a problem in that they are insoluble in saturated hydrocarbon solvents although they are soluble in aromatic hydrocarbon solvents and resultantly polymerization catalysts containing such complexes cannot be used for producing polymers using saturated hydrocarbon solvents.
In recognition of the situation, the objects of the present invention are to provide a complex, important from the industrial viewpoint, which has a high activity at reaction temperatures efficient in the industrial process for olefin polymerization and is soluble in saturated hydrocarbon solvents, and to provide a highly active olefin polymerization catalyst containing the complex, and a process for producing olefin polymers which uses the catalyst.